I was looking for some enclosure ideas for my Replicator 2 and It dawned on me that if you coated one side of a 'wall' with mylar you could use just about anything to create the enclosure walls.

You'll need a sheet of mylar. Mylar is very cheap. I found a 5ft by 6ft sheet of it for $2.99(USD) at Target packaged as an emergency blanket in the camping section. You should be able to find a similar product in a camping or military surplus store. Or you can just find out where the weather balloon people get theirs. I think you can flip around a helium party balloon also.

You'll also want to make them removable. I chose to use black velcro tape from a craft store for $5.99 USD.

Now find any sturdy material that you can cut into the proper shape to fit over the side holes. I used sheet of very stiff cardboard with a black side that shows through the hole. Like the box the Makerbot came in. The end result is surprisingly stock looking and I'm willing to bet the mylar makes for a better heat box than acrylic but I have not yet had a chance to prove it.

Now wrap the mylar around one side of your wall using the velcro tape to secure it. Put the other side of the velcro tape on the wall of the Makerbot around the side port holes and you have partial enclosure for less than 10 dollars US.